Current options concerning the endodontically-treated teeth restoration with the adhesive approach

3D-finite element analysis and weibull analysis of maxillary first molar restored with endocrowns with different pulpal extensions compared with conventional crowns with post-and-core

BACKGROUND

Rehabilitation of endodontically treated teeth with large coronal destruction is still a clinical challenge. No established guidelines specify where a conventional crown with fiber-reinforced composite (FRC) post-and-resin core or an endocrown (EC) is indicated and which material or pulpal extension should be used.

OBJECTIVE

To provide evidence for restoring severely damaged maxillary first molar (MFM) by comparing the fracture and debonding resistance after being restored with the ceramic EC and the conventional zirconia crown and FRC post-and-resin core.

METHOD

Models of a MFM with a mesial-occlusal-distal-palatal defect with different restoration strategies were created: C-FRC -- conventional crown with FRC post, EC-Zr-3/4/5 - zirconia EC with 3-/4-/5-mm pulpal extension, EC-Li-3/4/5 - lithium disilicate EC with 3-/4-/5-mm pulpal extension. Two loading conditions were applied: vertical loading - a 400-N force along the tooth's long axis; lateral loading - a 225-N force at a 45-degree angle buccally to the tooth's long axis. Three-dimensional finite element analysis and Weibull analysis were conducted for the above seven models.

RESULTS

The C-FRC group obtained the lowest maximal Mohr-Coulomb stress ratio (MσMC ratio) in the residual tooth structure under both loadings (0.2646 and 0.2815, respectively). The lowest MσMC ratio in the cement was in the EC-Li-5 group under both loadings (0.07660 and 0.3177, respectively). The lowest maximal shear stress at the adhesive interface was in the EC-Li-3 group under both loadings (5.700 MPa and 20.48 MPa, respectively).

CONCLUSIONS

The conventional crown with FRC post-and-resin core is still suitable for restoring a MFM with a mesial-occlusal-distal-palatal defect. Lithium disilicate EC with 3-mm pulpal extension may be a choice for the MFM where conventional restoration is not applicable.

Clinical Outcome and Predictors of Customized Polyetheretherketone Post-and-Cores for Residual Root and Crown: A Retrospective Study

OBJECTIVES

This retrospective, non-interventional study aimed to evaluate the longevity and factors influencing the success of custom-fabricated polyetheretherketone (PEEK) post-and-cores in endodontically treated teeth (ETT).

MATERIAL AND METHODS

During the observation period (2019-2022), 63 patients received 100 customized PEEK post-and-cores. Clinical outcomes were analyzed based on the following parameters: age, gender, tooth type, tooth position, proximal contacts, remaining cavity walls, antagonist contacts, and final restoration. Kaplan-Meier analysis was used for the survival probability. Log-rank tests were used to identify univariate associations between failure rates and other potential factors. Cox regression was used to assess the risk of failure and determine possible risks between the identified factors at a cut-off point p-value (0.25 in univariate analysis).

RESULTS

The median follow-up duration was 20.62 months, with a maximum of 40.57 months. 93 restorations were judged as successful and 99 teeth survived. The main failure type was decementation of the restoration (n = 4). The annual failure rate was 3.4%. Gender, remaining tooth structure, and final restoration were found to be correlated with success rates in the preliminary univariate analysis (Log-rank tests) to determine the association between failure rates and potential factors. Multifactorial survival analysis (Cox regression) showed that teeth with coronal walls had a significantly lower failure risk than deprived teeth, even with the ferrule effect. (HR = 0.04; 95% CI for HR = 0.01-0.29; p = 0.002).

CONCLUSIONS

PEEK post-and-cores adapt well to clinical restorative needs and offer favorable short-term clinical outcomes. The remaining cavity wall was a significant success rate predictor.

Influence of post material and ferrule thickness on the fracture resistance of endodontically treated premolars: A laboratory study

STATEMENT OF PROBLEM

The influence of the ferrule thickness and post materials on the fracture resistance of endodontically treated teeth remains unclear.

PURPOSE

The purpose of this laboratory study was to evaluate the influence of post material and ferrule thickness on the fracture resistance of endodontically treated mandibular premolars.

MATERIAL AND METHODS

Sixty-four extracted and endodontically treated mandibular first premolars were used and divided into 4 test groups (n=16) depending on the ferrule thickness: F-0: without a ferrule, F-0.5: with a 0.5-mm ferrule thickness, F-1: with a 1-mm ferrule thickness, and F-1.5: with a 1.5-mm ferrule thickness. In groups with ferrules, the height ranged from 2 mm buccally/lingually to 1 mm proximally. Teeth in subgroups (n=8) were restored with either prefabricated glass fiber (FF) or titanium posts (FT) (ISO size 70 and length of 7.5 mm) and then adhesively restored with composite resin foundation materials. After foundation procedures, each specimen was restored with a cobalt chromium crown which was cemented with glass ionomer cement. All specimens were subjected to dynamic loading in a masticatory simulator for 1 200 000 loading cycles with a nominal load of 5 Kg at 1.2 Hz and simultaneous thermocycling (5 to 55 °C). Specimens were then quasistatically loaded at 30 degrees in a universal testing machine until fracture. Fracture loads were analyzed by using 2-way ANOVA followed by the Tukey honestly significant difference test (α=.05).

RESULTS

Fracture loads ranged from 610 ±45 N (no ferrule - glass fiber post) to 1216 ±169 N (1.5 mm ferrule thickness - glass fiber post). A statistically significant increase in fracture resistance was observed with increasing ferrule thickness (P<.001). However, post materials did not show a statistically significant influence (P=.977).

CONCLUSIONS

Under the conditions of this laboratory study, increasing the ferrule thickness had a significant effect on the fracture resistance of endodontically treated teeth after thermomechanical fatigue, irrespective of post materials.

Mechanical performance of endocrown restorations in anterior teeth: A systematic review and network meta-analysis

OBJECTIVES

To conduct a systematic review and network meta-analysis (NMA) to answer whether endocrown restorations have similar mechanical behavior than other traditional core-crown systems with or without intracanal posts for the rehabilitation of anterior endodontically treated teeth.

METHODS

The review followed the PRISMA Extension Statement for NMA. Studies were identified by a systematic search to select reports on endocrown restorations in anterior teeth. A search was performed in PubMed (MEDLINE), Scopus, Web of Science, Embase, SciELO, and LILACS databases. Articles evaluating mechanical performance through in vitro and finite element analysis (FEA) studies were selected and the risk of bias was assessed using the RoBDEMAT and ROBFEAD tools, respectively. The data were analyzed qualitatively and quantitatively through NMA using the MetaInsight tool.

RESULTS

Eleven articles were included (eight in vitro and three with FEA design). Six in vitro studies were evaluated using NMA. Composite resin endocrowns showed greater load-to-fracture and lower occurrence of catastrophic failures than traditional restorations. Combining glass fiber post with composite restoration also showed good strength behavior. Regarding FEA studies, two out of three studies showed a more homogeneous distribution of stress for the endocrown group.

SIGNIFICANCE

Endocrowns performed similarly to or better than conventional restorative strategies, with composite resin being the most recommended material of choice. The rehabilitation of endodontically treated anterior teeth with extensive coronal destruction is typically challenging for the dentist, and there is still no consensus in the literature that provides conclusive answers for choosing the appropriate material and restorative strategy. Exploring new techniques and materials that make this procedure easier for the dentist and guarantee good results is paramount.

Fiberglass posts reduced fractures in endodontically treated teeth restored with veneers: a case-control study

This study aimed to evaluate the effects of fiberglass posts on fracture behavior in endodontically treated teeth (ETT) restored with composite veneers. Adult patients who had endodontically treated anterior teeth restored with composite veneers, with or without fiberglass posts, were divided into the case (with fractured teeth) and control (without fractured teeth) groups. All fracture patterns were sorted by a 6-point scoring system: 0, no fracture; 1, veneer buccal fracture; 2, incisal edge fracture; 3, coronal middle-third fracture; 4, coronal cervical fracture; 5, coronal and root fracture; and 6, root fracture. The odds ratio was calculated concerning the outcome (fracture) and exposed factor (post presence). Fracture patterns were analyzed by the Mann-Whitney and Fisher exact tests, with a significance level of 95%. Of the 89 ETT restored with composite veneers (31 with posts; 58 without posts), 30 were fractured. The odds ratio revealed a reduction in fracture risk to 34% compared with ETT without posts. Teeth without posts fractured more frequently, showing more complex fracture patterns. In conclusion, fiberglass posts decreased the risk of fractures in ETT restored with composite veneers.

Comparative Assessment of Post-Fatigue Resistance of Mandibular First Molars Restored With Polyether Ether Ketone and Lithium Disilicate Endocrowns

Background and Objectives: Contemporary dentistry focuses on more conservative treatment options such as endocrown restorations and application of dental materials with higher resemblance to tooth structure. Polyether ether ketone (PEEK) polymer is a material used for the fabrication of endocrowns. This study aimed to compare the post-fatigue resistance (PFR) of mandibular first molars restored with PEEK and lithium disilicate (LS2) endocrown restorations. Materials and Methods: This in vitro, experimental study was conducted on 20 human mandibular first molars with similar dimensions. The teeth were prepared for endocrown restoration and were assigned to two groups (n = 10) of PEEK and LS2 endocrowns. After fabrication by the computer-aided design and computer-aided manufacturing (CAD-CAM) technique, the restorations were cemented with resin cement. Next, the teeth underwent 15,000 thermal cycles followed by cyclic loading with 600,000 cycles of compressive force (100 N, 4 Hz) and were then subjected to compressive load application in a universal testing machine. The load causing endocrown failure was recorded as the PFR of the respective restoration. The failure mode was also inspected under a light microscope. Data were analyzed by the independent t-test and also chi-square, Mann-Whitney, and Fisher's exact tests (α < 0.05). Results: The teeth with PEEK endocrowns showed significantly higher PFR than those with LS2 endocrowns. Irreparable fractures were dominant in both groups. Conclusion: PEEK may serve as a suitable alternative to LS2 for the fabrication of endocrown restorations.

Compressive Stress in Teeth Restored with Endocrown and Build-up: A Finite Element Analysis

AIM

This study evaluates compressive stress in teeth restored with endocrown (ECW) and build-up (BUP) using finite element analysis (FEA). Understanding stress distribution in dental restorations is crucial for improving treatment outcomes and longevity.

MATERIALS AND METHODS

A second lower molar was modeled using Solidworks® (Version 2017). The ECW was simulated with nanoceramic resin, while the BUP included a core and nanoceramic crown. Mechanical properties, including modulus of elasticity, Poisson's ratio, and tensile strength were assigned to materials. Axial and oblique loads of 900N were applied, and stress was analyzed using Solidworks®.

RESULTS

Results indicated that under axial loading, ECW experienced a maximum stress of 91.9 MPa, significantly higher than BUP's 49 MPa. Under oblique loading, ECW exhibited 132 MPa compared with 116 MPa in BUP. The highest stress concentration was in the cervical area, where ECW showed greater stresses in both the substrate and restored area. Build-up demonstrated better stress distribution and lower fracture risk.

CONCLUSION

Endocrown restoration results in higher compressive stresses, especially in the cervical region, which may increase the risk of fracture. Conversely, the BUP technique, which preserves cervical dentin, offers improved stress distribution and reduced fracture risk, making it a more robust solution for endodontic rehabilitation.

CLINICAL SIGNIFICANCE

This study underscores the importance of selecting appropriate restoration methods to minimize stress and enhance the longevity of dental treatments, ultimately leading to better patient outcomes. How to cite this article: Bardales-Espinoza KA, Mora-Ipince AR, Chávez-Méndez MA, et al. Compressive Stress in Teeth Restored with Endocrown and Build-up: A Finite Element Analysis. J Contemp Dent Pract 2024;25(11):1027-1033.

A Fluorescence-based Method to Reaccess Root Canals in Endodontically Treated Teeth: A Micro-Computed Tomography Tridimensional Assessment

INTRODUCTION

The aim of this study was to evaluate the volume of dentin removal and the volume of remnants of restorative material after the removal of an esthetic restorative coronal set and cervical barrier in endodontically treated mandibular molars with the aid of different magnification methods using 3-dimensional (3D) micro-computed tomographic (micro-CT) morphometric analysis.

METHODS

A sample of 30 mandibular first molars (N = 30) was used. All teeth were endodontically treated, and the specimens were initially scanned using micro-CT imaging and reconstructed. The molars were filled by a single-cone technique, and immediately the material at the initial 2-mm cervical level was removed. Cervical barriers were confected using ionomer glass cement with fluorescein 0.1%, filling the 2 mm at the cervical level of the canals and an additional 2 mm as the base. The coronal restoration set was performed using esthetic resin composites. A simulated tooth aging process was performed with 20,000 thermocycling cycles. The sample was distributed into the following 3 groups (n = 10) for the removal of the restoration set and cervical barrier with diamond burs based on the magnification aid: no magnification aid (naked eye), operative microscope aid, and REVEAL device (Design for Vision Inc, Bohemia, NY) aid. After removal, the final 3D micro-CT scanning and reconstruction were conducted with the same parameters as the initial scanning, and superposition of the final and initial scanning was performed. Morphometric analysis was conducted using CTAn software (Bruker microCT, Kontich, Belgium) to assess the volume of remnant restorative material (mm³), the volume of dentin removal (mm³), and the direction and site of dentin removal. Data were analyzed using 1-Way analysis of variance (P < .05).

RESULTS

The REVEAL group showed better results regarding the volume of remnant material (3.17 ± 1.65) and the percentage of dentin removal (2.56 ± 1.34). The microscope group showed no statistical difference compared with the REVEAL group regarding dentin removal (3.30 ± 1.48) and was statistically similar to the naked eye group in the volume of remnant material (9.63 ± 4.33). The naked eye group showed the worst results for the volume of remnant material (7.60 ± 2.68) and the percentage of dentin removal (6.60 ± 3.70).

CONCLUSIONS

The use of fluorescence associated with magnification was the method that presented the best results, with lower percentages of dentin removal and smaller volumes of remaining restorative material. This is an innovative technology in endodontics that shows potential to overcome the challenge of reaccessing root canals in the context of endodontic retreatment.

Evaluation of colour change, marginal adaptation, fracture strength, and failure type in maxillary and mandibular premolar zirconia endo-crowns

OBJECTIVES

The objective of this in vitro study was to evaluate the effects of different preparation designs on the mean colour change (ΔE*), marginal adaptation, fracture resistance, and fracture types of maxillary and mandibular premolar endocrowns (ECs).

METHODOLOGY

A total of 40 extracted maxillary and mandibular premolars were treated endodontically, and each type was subdivided according to the remaining axial height (remaining walls on all surfaces; 2-4 mm) and 2 mm inside the pulp chamber. Specimens were immersed in coffee for 14 days, ΔE* was determined, marginal adaptation was observed, fracture forces test was conducted, and the samples were examined visually at 10× magnification to evaluate failure type and identify fracture origin. The data were entered and analyzed using Statistical Package for Social Sciences, and significance between and within groups was evaluated through ANOVA. The p-value ≤ 0.05 was considered statistically significant.

RESULTS

The ΔE* values of the maxillary premolar with 2 mm axial height were the highest (6.8 ± 0.89 units), whereas the lowest value was observed in the mandibular premolar with 4 mm axial height (2.9 ± 0.53 units). Significant differences (p < 0.05) in teeth and design were observed. The marginal adaptation of the mandibular premolar with 4 mm axial height was the highest (30.20 ± 1.53 μm), whereas the lowest marginal adaptation was observed in the maxillary premolar with 2 mm axial height (14.38 ± 0.99 μm), and the difference was statistically significant (p < 0.05). The maximum fracture force was observed in maxillary premolars with 2 mm axial height (2248.15 ± 134.74 N), and no statistically significant difference (p = 0.07) was observed between maxillary and mandibular premolars at 4 mm axial height.

CONCLUSION

The recorded ΔE* values of the ECs were within clinically acceptable values or slightly higher, and the marginal adaption values were within acceptable and recommended clinical values in µm. EC preparation with 2 mm axial height in both arches recorded the highest fracture forces. Type III (split fracture) failure was recorded as the highest in the maxillary and mandibular premolar ECs with different axial wall heights.

Direct Versus Indirect Treatment Options of Endodontically Treated Posterior Teeth: A Narrative Review

One of the controversial topics in dentistry is restoring endodontically treated posterior teeth. Most posterior teeth that undergo endodontic treatment are subjected to a high rate of fracture due to excessive amount of loss of tooth structure. The aim of this review is to evaluate and compare the restorative and prosthetic treatment options to provide clinical recommendations for restoring endodontically treated posterior teeth. Both Medline on PubMed and Google Scholar were utilized for the search. The terms on our keyword list were "crown," "onlay," "endo-crown," "amalgam," and "composite," with the time frame from 1977 to 2024. We also examined the reference lists of potentially relevant papers for any recent review articles. Our analysis examined review articles found through computerized searches, along with relevant citations from the bibliographies of those studies. This review will focus on the dental restorative options and the amount of remaining tooth structure in determining the final restoration of an endodontically treated posterior tooth. This narrative review addresses different treatment options for endodontically treated posterior teeth based on the amount of remaining tooth structure. In addition, it compares the survival rate and the limitations among direct and indirect restorations.

Knowledge and Practice of Endocrown Restorations Among Dental Students and Dentists in Sirte, Libya

Background Restoring endodontically treated teeth has long posed a challenge for clinicians. The endocrown (EC) is an innovative and conservative restoration designed for teeth with severely damaged coronal structures. ECs offer performance that is equivalent to or even exceeds that of traditional post-core-crown treatments. Purpose This web-based cross-sectional survey aimed to evaluate the level of knowledge and practical experience regarding ECs as post-endodontic prostheses among dental students and practitioners in Libya. Methods A 22-item structured questionnaire was created using Google Forms and distributed to final-year students, interns, faculty at the College of Dentistry at Sirte University, and practicing dentists in Libya. The sample comprised 290 participants. The questionnaire was divided into three sections: the first assessed demographic variables such as gender, education level, country of graduation, and workplace; the second evaluated knowledge of ECs through 11 questions; and the third focused on EC practice, also comprising 11 questions. Statistical analysis was conducted using IBM SPSS Statistics for Windows, Version 21.0 (Released 2012; IBM Corp., Armonk, NY, USA). Results A total of 50.7% of participants indicated that EC restorations are suitable for molar teeth, 41.4% noted that a butt joint finish line is used for EC preparation, and 66.9% preferred all-ceramic materials for ECs. Nearly 72.8% reported that computer-aided design/computer-aided manufacturing technology is employed for EC fabrication. Additionally, 61.7% agreed that EC designs offer higher fracture resistance compared to conventional crowns. Despite this, 64.5% of participants had not cemented an EC in their clinic in recent years. Significant differences in knowledge and practice regarding ECs were observed across various factors, including gender, education level, country of graduation, and workplace. Conclusion Most participants demonstrated an acceptable level of knowledge and practical experience with EC restorations. Therefore, incorporating ECs as a major topic in the postgraduate prosthodontics curriculum is recommended.

Suitability of Direct Resin Composites in Restoring Endodontically Treated Teeth (ETT)

(1) Background: The in vitro study aimed to investigate mechanical characteristics of resin composites and their suitability in direct restauration of endodontically treated teeth (ETT). (2) Methods: 38 endodontically treated premolars with occlusal access cavities were directly restored using the following resin composites and adhesives: Tetric Evo Ceram® + Syntac classic® (n = 10), Venus Diamond® + iBond Total-Etch® (n = 10), Grandio® + Solobond M® (n = 9), Estelite® Sigma Quick + Bond Force® (n = 9). After thermocycling, the elastic modulus, shear-bond-strength, fracture load (Fmax) and fracture mode distribution were evaluated. Statistical analysis: one-way ANOVA, t-test, Kruskal-Wallis test; p < 0.05. (3) Results: Grandio® showed the highest E-modulus (15,857.9 MPa) which was significant to Venus Diamond® (13,058.83 MPa), Tetric Evo Ceram® (8636.0 MPa) and Estelite® Sigma Quick (7004.58 MPa). The highest shear-bond-strength was observed for Solobond M® (17.28 MPa), followed by iBond® (16.61 MPa), Syntac classic® (16.41 MPa) and Bond Force® (8.37 MPa, p < 0.05). The highest fracture load (Fmax) was estimated for ETT restored with Venus Diamond® (1106.83 N), followed by Estelite® Sigma Quick (1030.1 N), Tetric Evo Ceram® (1029 N) and Grandio® (921 N). Fracture-mode distribution did not show any significant differences. (4) Conclusions: The observed resin composites and adhesives show reliable mechanical characteristics and seem to be suitable for direct restoration of endodontically treated teeth.

Biomechanical impact of labiolingual diameter on endodontically treated anterior teeth with crown restoration under occlusal loading

OBJECTIVE

To evaluate the effect of the labiolingual diameter and construction of an endodontically treated (ET) anterior tooth with crown restoration on stress distribution and biomechanical safety under occlusal loading.

METHODOLOGY

Three-dimensional finite element models were generated for maxillary central incisors with all-ceramic crown restorations. The labiolingual diameters of the tooth, defined as the horizontal distance between the protrusion of the labial and lingual surfaces, were changed as follows: (D1) 6.85 mm, (D2) 6.35 mm, and (D3) 5.85 mm. The model was constructed as follows: (S0) vital pulp tooth; (S1) ET tooth; (S2) ET tooth with a 2 mm ferrule, restored with a fiber post and composite resin core; (S3) ET tooth without a ferrule, restored with a fiber post and composite resin core. A total of 12 models were developed. In total, two force loads (100 N) were applied to the crown's incisal edge and palatal surface at a 45° oblique angle to the longitudinal axis of the teeth. The Von Mises stress distribution and maximum stress of the models were analyzed.

RESULTS

Regardless of the loading location, stress concentration and maximum stress (34.07~66.78MPa) in all models occurred in the labial cervical 1/3 of each root. Both labiolingual diameter and construction influenced the maximum stress of the residual tooth tissue, with the impact of the labiolingual diameter being greater. A reduction in labiolingual diameter led to increased maximum stress throughout the tooth. The ferrule reduced the maximum stress of the core of S2 models (7.15~10.69 MPa), which is lower compared with that of S3 models (19.45~43.67 MPa).

CONCLUSION

The labiolingual diameter exerts a greater impact on the biomechanical characteristics of ET anterior teeth with crown restoration, surpassing the influence of the construction. The ferrule can reduce the maximum stress of the core and maintain the uniformity of stress distribution.

The influence of Zircos-E® etchant, silica coating, and alumina air-particle abrasion on the debonding resistance of endocrowns with three different preparation designs

OBJECTIVES

The study aimed to evaluate the debonding resistance of three different endocrown designs on molar teeth, using three different zirconia surface pretreatments.

MATERIAL AND METHOD

Ninety human mandibular first molars were divided into three main groups: endocrowns without ferrule, with 1 mm ferrule, and with 2 mm ferrule. The subgroups were defined by their surface pretreatment method used (n = 15): 50 μm alumina air-particle abrasion, silica coating using 30 μm Cojet™ particles, and Zircos-E® etching. The endocrowns were fabricated using multilayer zirconia ceramic, cemented with self-adhesive resin cement, and subjected to 5000 thermocycles (5-55°C) before debonding. The data obtained were analyzed using a two-way ANOVA.

RESULTS

All test specimens survived the thermocyclic aging. The results indicated that both the preparation design and the surface treatment had a significant impact on the resistance to debonding of the endocrowns (p < .001). The 2 mm ferrule followed by the 1 mm ferrule designs exhibited the highest debonding resistance, both were superior to the endocrown without ferrule. Zircos-E® etching and silica coating yielded comparable debonding resistance, which were significantly higher than alumina air-particle abrasion. All endocrowns demonstrated a favorable failure mode.

CONCLUSIONS

All designs and surface treatments showed high debonding resistance for a single restoration. However, ferrule designs with Zircos-E® etching or silica coating may represent better clinical options compared to the nonferrule design or alumina airborne-particle abrasion. Nonetheless, further research, including fatigue testing and evaluations with different luting agents is recommended.

Augmented Reality Head-Mounted Device and Dynamic Navigation System for Postremoval in Maxillary Molars

INTRODUCTION

This study evaluates the feasibility of an augmented reality (AR) head-mounted device (HMD) displaying a dynamic navigation system (DNS) in the surgical site for fiber postremoval in maxillary molars and compares it to the DNS technique.

METHODS

Fifty maxillary first molars were divided into 2 groups: AR HMD + DNS (n = 25) and DNS (n = 25). The palatal canal was restored with RelyX fiber post (3M ESPE) luted with RelyX Unicem (3M ESPE). A core buildup was performed using Paracore (Coltene/Whaledent). Cone beam computed tomography (CBCT) scans were taken before and after postremoval. The drilling trajectory and depth were planned under X-guide software (X-Nav Technologies, Lansdale, PA). For the AR HMD + DNS group, the AR HMD (Microsoft HoloLens 2) displayed the DNS in the surgical site. The three dimensional (3D) deviations (Global coronal deviation [GCD] and global apical deviation [GAD]) and angular deflection (AD) were calculated. The number of mishaps and operating time were recorded.

RESULTS

Fiber post was removed from all samples (50/50). The AR HMD + DNS was more accurate than DNS, showing significantly lower GCD and GAD deviations and AD (P < .05). No mishap was detected. The AR HMD + DNS was as efficient in time as DNS (P > .05).

CONCLUSIONS

Within the limitations of this in vitro study, the AR HMD can safely display DNS in the surgical site for fiber post-removal in maxillary molars. AR HMD improved the DNS accuracy. Both AR HMD + DNS and DNS were time-efficient for fiber postremoval in maxillary molars.

Long-term performance of ceramic in/-onlays vs. cast gold partial crowns - a retrospective clinical study

OBJECTIVES

To assess the long-term clinical performance of ceramic in-/onlays (CIOs) and cast gold partial crowns (CGPCs) in posterior teeth in terms of success, survival, complications (biological, technical) and quality.

MATERIAL AND METHODS

In a retrospective study, a total of 325 patients were recorded after up to 24.8 years (mean 13.9 ± 3.8 years) having (pre-)molars restored with CIO (Empress I, Ivoclar Vivadent, n = 161) and CGPC (Degunorm, DeguDent, n = 164) by supervised undergraduate students. A total of 296 restorations were assessed clinically and radiologically in healthy and endodontically treated teeth using modified United States Public Health Service (USPHS) criteria. Cumulative success and survival rates of the restorations were calculated using Kaplan-Meier estimates. Biological and technical complications were recorded. Status of oral health comprising caries risk and localized periodontitis were assessed.

RESULTS

The cumulative success rates of CIOs were 92.1% and of CGPCs 84.2% after mean service times of 14.5 years. The annual failure rates of total service times were 0.5% in teeth restored with CIO (n = 155) and 0.7% in teeth restored with CGPC (n = 163). The cumulative survival rates of CIOs were 93.9% after a mean service time of 15.2 years and decreased to 91.7% after 23.5 years. The cumulative survival rates of CGPCs were 92.6% after a mean service time of 14.9 years and 91.8% after 23.5 years. Complications in CIOs (n = 149) were ceramic fracture (6.7%), secondary caries (4.7%), endodontic complication (2.7%) and tooth fracture (1.3%) compared to CGPCs (n = 147) with endodontic complication (8.8%), secondary caries (4.8%) and decementation (2.0%). Endodontically treated teeth restored with CIO or CGPC revealed significantly less often success compared with corresponding vital teeth (p = .02). CIOs and CGPCs revealed clinically and radiographically good and excellent qualities with 71.8% (107/149) and 68% (100/147) without any significant differences regarding type of restoration.

CONCLUSIONS

Both CIOs and CGPCs achieved high survival rates up to 24.8 years when performed by supervised undergraduate students. The longevity of the restorations may benefit from the intraoral repair of accessible defects and, in case of pulp infection or necrosis, an adequate endodontic management.

CLINICAL RELEVANCE

CIOs and CGPCs made by supervised undergraduate students are proper restoration types in posterior teeth in the long-term. An adequate preparation design, meticulous care in the inserting technique and constant biofilm removal due to proper oral hygiene combined with professional maintenance care are substantial. The clinical long-term performance was mostly limited by ceramic fractures in CIOs and endodontic complications in CGPCs.

The fracture strength and the failure mode of lithium disilicate or resin nano ceramics as a crown, overlay, or endocrown restoration on endodontically treated teeth

INTRODUCTION

Different materials and restorative concepts have been proposed over the years to restore endodontically treated teeth (ETT). Monolithic ceramic and composite restoration can be lute to the tooh, without the use of a post. However, little is known how the material stiffness and presence of a composite core will affect the survival and failure mode. The objective of this in-vitro study was to evaluate the fracture strength and failure mode of endodontically treated molars, restored with ceramic or hybrid composite monolithic restoration, in the presence of absence of a composite core.

MATERIALS AND METHODS

Sixty depulped molars were restored with a lithium-disilicate (e.max CAD) or hybrid composite (Cerasmart) restoration. Both materials were used in a monolithic approach, but with 3 different designs: (a) monolithic endocrown, (b) crown with a separate composite core, and (c) overlay without core buildup or pulpal extension. Ten sound teeth were used as control group. All groups were thermocycled (10,000 cycles), subsequently loaded in a chewing simulator (100,000 cycles) and finally loaded until fracture.

RESULTS

Peak fracture loads and failure modes were registered. No significant differences were seen between the groups in terms of fracture load. Failure modes were statistically significantly different among groups with significant correlation between restoration type and material. (p < 0.001 and p = 0.033, respectively). No group presented significantly higher fracture resistance. Although ceramic crowns and overlays presented the highest repairability, all restored ETT were within the range of the intact tooth' fracture strength.

CONCLUSION

No restoration presented significant different fracture loads. However, the type of restoration and material choice were correlated to the fracture mode.

Fracture resistance and fracture modes in endodontically treated maxillary premolars restored using different CAD-CAM onlays

PURPOSE

To examine the fracture resistance and fracture modes of endodontically treated teeth (ETT) restored using onlays of different materials fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM).

METHODS

Sixty maxillary first premolars were randomly assigned to six groups (n=10). The first group comprised intact teeth (INT). The remaining premolars were prepared for mesio-occluso-distal cavity and root canal treatments. Group 2 was treated using polymer-reinforced zinc oxide-eugenol intermediate restorative material (IRM). Groups 3-6 were core build-up, prepared for onlay, and restored using resin nanoceramic (Cerasmart [CER]), polymer-infiltrated ceramic networks (Vita Enamic [VE]), lithium disilicate-based ceramic (IPS e.max CAD [EM]), or translucent zirconia (Katana Zirconia UTML [KZ]). All specimens were immersed in 37 °C distilled water for 24 h. Each specimen was loaded at 45° to the long axis until failure (crosshead speed, 0.5 mm/min). Fracture loads were analyzed using one-way analysis of variance and Tukey's post-hoc test (α=0.05).

RESULTS

There were no significant differences in fracture load among the INT, CER, VE, and EM groups. The fracture load in the KZ group was significantly higher than those in the other groups (P < 0.05). Fracture load was the lowest in the IRM group (P < 0.05). The unrestorable failure rate was 70% in the KZ group and 10-30% in the other experimental groups.

CONCLUSIONS

ETT restored using Cerasmart, Vita Enamic, or IPS e.max CAD onlays had fracture resistance and patterns comparable to those of intact teeth. Katana Zirconia UTML-restored ETT had the highest fracture load but also a higher unrestorable failure rate.

Effect of cervical margin relocation on marginal adaptation and microleakage of indirect ceramic restorations

PURPOSE

This study evaluated the effect of cervical margin relocation (CMR) with two different materials and contamination with hemostatic agents on the margin adaptation and microleakage of ceramic restorations.

MATERIALS AND METHODS

Mesial-occlusal-distal cavities were prepared in 60 human first molars and distributed to 3 groups (n = 20) according to the margin relocation procedure. The groups were: group F; flowable composite applied in two 2 mm increments, group B; bulk-fill flowable composite applied as a bulk increment of 4 mm thickness and group C (control); no CMR was done. Each group was subdivided into two subgroups (subgroup N; no hemostatic agent applied and subgroup H; hemostatic agent was applied). In all groups, ceramic inlays were prepared and cemented. The samples were subjected to thermocycling (10,000 cycles). The adaptation of the cervical margin was evaluated with scanning electron microscopy (200×). Samples were then assessed for microleakage analysis with the dye penetration method. Marginal adaptation data were normally distributed and analyzed using two-way ANOVA followed by Tukey's post hoc test. Ordinal microleakage score data were analyzed using cumulative link models followed by the analysis of deviance using Wald chi-square tests.

RESULTS

Both CMR and contamination with a hemostatic agent had significant effects on the margin adaptation of the cervical margin. Group C showed the highest adaptation with no significant difference from group F. The lowest adaptation was revealed in group B with a significant difference from group C. Subgroup N (in all groups) showed a statistically higher adaptation than subgroup H. Regarding microleakage assessment, CMR had no significant effect but hemostatic agent application showed a significantly higher microleakage score for all groups.

CONCLUSIONS

Both the CMR procedure and contamination with AlCl3 hemostatic agent had a negative effect on marginal adaptation. For microleakage assessment, only contamination with hemostatic agent negatively affected the microleakage with no effect on the margin relocation procedure.

Single crown vs. composite for glass fiber post-retained restorations: An 8-year randomized clinical trial

OBJECTIVES

This study aimed to compare the success and survival rates of metal-ceramic crowns and composite resin restorations applied in root filled teeth that received a glass fiber post.

METHODS

A prospective, randomized controlled trial, with equivalent parallel groups was designed. Eighty-two teeth were randomly allocated to the metal-ceramic or composite resin groups. Multivariate Cox regression analysis with shared frailty for patients and Kaplan-Meier curves were performed using success and survival rates (p<0.05).

RESULTS

Seventy-five post-retained restorations (34 metal-ceramic crowns and 41 composite restorations) in 62 patients were analyzed. The median follow-up was 8.1 years [IQR 4.0-9.9]. Twenty-seven failures were observed. Twenty-two failures (81.5 %) were observed in the composite resin group, of which six (27.3 %) were not repairable. Five failures (18.5 %) were observed in the metal-ceramic crown group, of which three (66.6 %) were non-repairable. The cumulative success rate at 8 years was 85.0 % for crowns (AFR=1.31 %) and 43.2 % for composite resins (AFR=6.58 %), while the survival rate was 93.8 % for crowns (AFR=0.52 %) and 97.6 % for composite resins (AFR=0.20 %). Considering the success rates, adjusted multivariate Cox regression showed that composite resin had a Hazard Ratio of 5.07 (95 %CI, 1.99-12.89) greater than the metal-ceramic crown. No significant difference in the failure risk was observed when the survival rates were considered (HR=0.38, 95 %CI (0.10 - 1.44), p = 0.156). Co-variables did not affect the success and survival rates (p>0.05).

CONCLUSIONS

Metal-ceramic crowns showed a higher success rate than composite restorations. The survival rates were similar, but composite restorations presented a higher need for repairs.

CLINICAL SIGNIFICANCE

Post-retained composite restorations may need more reinterventions during the lifecycle, although more preservation of sound tooth structure is expected with a large restoration of resin post-and-core. These aspects have to be discussed with the patient for decision-making planning.

Impact of CAD/CAM Material Thickness and Translucency on the Polymerization of Dual-Cure Resin Cement in Endocrowns

The objective of this study is to evaluate the impact of the thickness and translucency of various computer-aided design/computer-aided manufacturing (CAD/CAM) materials on the polymerization of dual-cure resin cement in endocrown restorations. Three commercially available CAD/CAM materials-lithium disilicate glass (e.max CAD), resin composite (CERASMART), and a polymer-infiltrated ceramic network (ENAMIC)-were cut into plates with five different thicknesses (1.5, 3.5, 5.5, 7.5, and 9.5 mm) in both high-translucency (HT) and low-translucency (LT) grades. Panavia V5, a commercial dual-cure resin cement, was polymerized through each plate by light irradiation. Post-polymerization treatment was performed by aging at 37 °C for 24 h under light-shielding conditions. The degree of conversion and Vickers hardness measurements were used to characterize the polymerization of the cement. The findings revealed a significant decrease in both the degree of conversion and Vickers hardness with increasing thickness across all CAD/CAM materials. Notably, while the differences in the degree of conversion and Vickers hardness between the HT and LT grades of each material were significant immediately after photoirradiation, these differences became smaller after post-polymerization treatment. Significant differences were observed between samples with a 1.5 mm thickness (conventional crowns) and those with a 5.5 mm or greater thickness (endocrowns), even after post-polymerization treatment. These results suggest that dual-cure resin cement in endocrown restorations undergoes insufficient polymerization.

Evaluation of the Fracture Resistance of Different Designs of All-Resin Post and Core Systems: An In Vitro Study

Introduction There is a growing demand for post and core systems that offer both ease of use and efficiency. Recently introduced dual-cure build-up and post cement materials exhibit properties similar to dentin. The objective of this laboratory experiment is to compare the fracture resistance among three distinct post and core systems and identify the locations of failures within each group. Material and methods This in vitro experimental study involved 30 epoxy resin-based blocks (Endo Training Bloc J, Dentsply Sirona, Ballaigues, Switzerland) divided into three groups: The first group was a post space preparation and restoration with a fiber post (RelyX™ Fiber Post, 3M ESPE, Saint Paul, Minnesota, United States) 1.6 mm in diameter and 10 mm in length (Group A) where core build-up and cementation were performed using a dual-cure build-up and cement for endodontic post resin material (Core X Flow, Dentsply DeTrey, Konstanz, Germany). The second group was a post space preparation and restoration using a dual-cure build-up and cement for endodontic post resin material, 10 mm in length filled with resin but without fiber post placement (Group B). The third group was where post space and core were filled and restored with a dual-cure build-up and cement for endodontic post resin material, 5 mm in length and without fiber post placement (Group C). Subsequently, samples were mounted and tested using a universal testing machine (Instron, Canton, Massachusetts, United States), and the fracture site was located. Results Significant differences were identified among the three groups, indicating the impact of both post length and type on fracture resistance (p-value <0.05). Group B exhibited the highest mean compressive strength resistance and maximum load at 899.3330 (N), followed by Group C at 848.9690 (N) and Group A at 751.9620 (N). The predominant failures in the samples were core fractures or debonding of the core material. Conclusion All-resin posts demonstrated high fracture resistance, unlike fiber posts which displayed inferior fracture resistance.

Biomechanical performance of endocrown and core-crown restorations: A systematic review

OBJECTIVE

To assess and compare, through a systematic review of the literature, the biomechanical performance of endocrowns and traditional core-crowns (with and without intracanal post) for the rehabilitation of endodontically treated teeth with severe coronal structure damage.

MATERIALS AND METHODS

A systematic search was performed in MEDLINE/PubMed, Scopus, and Web of Science databases. In-vitro studies comparing endocrowns with (post-)core-crown restorations were selected and screened by two independent reviewers. The included studies were submitted to the risk of bias analysis using the RoBDEMAT tool and the biomechanical outcomes were collected for qualitative analysis. The extracted data were presented based on comparative analyses among the included studies.

RESULTS

Thirty-one studies were included: 9 studies evaluated restorations of molars, 14 for premolars, and 8 studies evaluated anterior restorations. For the majority of the studies, endocrowns showed either similar or greater survival rates under fatigue and monotonic load than (post-)core-crown restorations, irrespectively of the tooth. The endocrowns showed more favorable failure patterns than (post-)core-crowns, irrespectively of the tooth. Endocrowns produced lower stresses in the restorative material for molars and premolars and in the luting material for premolars than (post-)core-crown restorations. The included studies presented adequate information for most items of the RoBDEMAT risk of bias tool.

CONCLUSION

Endocrowns showed similar or greater biomechanical performance than the traditional (post-)core-crown restorations in most of the evaluated studies.

CLINICAL SIGNIFICANCE

This systematic review showed that endocrowns present either similar or greater biomechanical performance than core-crown restorations for anterior and posterior endodontically treated teeth with severe structural damage.

Fatigue and failure analysis of restored endodontically treated maxillary incisors without a dowel or ferrule

STATEMENT OF PROBLEM

Information on the survival and mode of failure of endodontically treated incisors without a ferrule and restored without dowels is lacking.

PURPOSE

The purpose of this in vitro study was to compare the survival and failure mode of endodontically treated incisors without a ferrule and restored with bonded ceramic crowns and various composite resin foundation restorations without dowels with a control group with fiber dowels.

MATERIAL AND METHODS

Forty-five decoronated endodontically treated bovine incisors without ferrule were divided into 3 experimental groups and restored with different adhesive foundation restorations without dowel: nanohybrid composite resin (Nd), bulk-fill composite resin foundation restoration (NdB), and fiber-reinforced bulk-fill composite resin (NdFR). A control group with conventional foundation restorations (glass-fiber dowel with nanohybrid composite resin foundation restoration without ferrule) (D) was included for comparison. All teeth were prepared to receive bonded lithium disilicate ceramic crowns luted with dual-polymerizing composite resin cement and were subjected to accelerated fatigue testing. Cyclic isometric loading was applied to the incisal edge at an angle of 30 degrees and a frequency of 5 Hz, beginning with a load of 100 N (5000 cycles). A 100-N load increase was applied each 15 000 cycles. Specimens were loaded until failure or to a maximum for cycles endured of 1000 N (140 000 cycles). Groups were compared by using the Kaplan-Meier survival analysis (log rank test at α=.05 and pairwise post hoc comparisons) and life table analysis for load-at-failure (followed by Wilcoxon pairwise comparison α=.05).

RESULTS

All the specimens failed before 140 000 load cycles. Even though no statistically significant differences were found between the experimental groups without dowel (P>.127), the fiber-reinforced foundation restoration yielded the highest mean ±standard deviation cycles to failure (46 023 ±4326) compared with Nd (38 899 ±2975) and NdB (39 751 ±2998). NdFR, however, outperformed the foundation restoration with glass-fiber dowel (35 026 ±2687) (P<.05). Most failure in groups without dowel were restorable, while 100% of catastrophic failure (unrestorable) were found in the group with dowels.

CONCLUSIONS

Based on the present in vitro study, dowels did not improve the performance of the adhesive restoration of endodontically treated incisors without a ferrule. The use of a short fiber-reinforced composite resin foundation restoration without a dowel was able to not only improve the resistance of the restorations compared with adhesive foundation restorations with dowels but also minimize catastrophic failures.

Monomer release, cell adhesion, and cell viability of indirect restorative materials manufactured with additive, subtractive, and conventional methods

PURPOSE

The aim of this study was to measure residual monomer, cell adhesion, and cell viability of 3-dimensional printable permanent resin (PR), hybrid ceramic block (HCB), and indirect composite (IC) produced with additive, subtractive, and conventional techniques.

METHODS

Five 8 × 8 × 2 mm3 samples of each material were prepared for each experiment. In a 24-h period, monomer release was analyzed with high-performance liquid chromatography, and cell viability and adhesion were evaluated with the water-soluble tetrazolium salt test. Data were analyzed with IBM SPSS Statistics 26.0 statistical software, and results were regarded as significant at α = 0.05.

RESULTS

Monomer release (triethylene glycol dimethacrylate, urethane dimethacrylate, and Bisphenol A glycerolate dimethacrylate) was significantly higher in the IC group. Mean cell viability was significantly lower in the HCB group than in the IC group.

CONCLUSION

All monomers in the tested materials were released at rates that were below clinical significance. Cell adhesion rates in the groups were similar. Cytotoxic response was classified as minor in the HCB and PR groups and non-cytotoxic in the IC group.

Expert consensus on digital guided therapy for endodontic diseases

Digital guided therapy (DGT) has been advocated as a contemporary computer-aided technique for treating endodontic diseases in recent decades. The concept of DGT for endodontic diseases is categorized into static guided endodontics (SGE), necessitating a meticulously designed template, and dynamic guided endodontics (DGE), which utilizes an optical triangulation tracking system. Based on cone-beam computed tomography (CBCT) images superimposed with or without oral scan (OS) data, a virtual template is crafted through software and subsequently translated into a 3-dimensional (3D) printing for SGE, while the system guides the drilling path with a real-time navigation in DGE. DGT was reported to resolve a series of challenging endodontic cases, including teeth with pulp obliteration, teeth with anatomical abnormalities, teeth requiring retreatment, posterior teeth needing endodontic microsurgery, and tooth autotransplantation. Case reports and basic researches all demonstrate that DGT stand as a precise, time-saving, and minimally invasive approach in contrast to conventional freehand method. This expert consensus mainly introduces the case selection, general workflow, evaluation, and impact factor of DGT, which could provide an alternative working strategy in endodontic treatment.

Enhancing the mechanical stability of restored teeth with interfacial cracks: Finite element analysis

OBJECTIVES

This study aims to enhance the mechanical stability of restored molar teeth with class II occlusal-distal (OD) cavities. We seek to achieve this goal through a comprehensive investigation of three primary factors: (1) the choice of restoration material properties, (2) internal cavity geometries, and (3) the impact of double-layered restoration configurations.

METHODS

To achieve our objectives, we initiated by creating two-dimensional (2D) models of restored teeth featuring class II OD cavities, utilizing scanned and segmented images of maxillary molar teeth. We drew 2D profiles of dentine and enamel, which were then imported into finite element analysis (FEA) software. To explore various cavity geometries, we implemented a total of thirteen different designs, encompassing straight, oblique, grooved, curved, and double-layered configurations. We utilized a semi-circular stone to simulate the application of contact load on the restored tooth. We applied identical boundary conditions and contact loading across all models. To assign material properties, we developed a Python code, enabling the automatic assignment of seven elastic moduli ranging from 2 GPa to 26 GPa to the restoration materials. Meanwhile, constant material properties were assigned to the enamel and dentine. In total, we conducted 133 FEA simulations to comprehensively analyse the effects of the aforementioned factors on the strength and performance of restored molar teeth.

RESULTS

Our analysis revealed two key factors significantly influencing the mechanical resistance of treated teeth, particularly in the presence of a crack or debonding: (1) the marginal geometry of the OD cavity and (2) the elastic modulus of the restorative material. However, altering the internal cavity angle and implementing a double-layered restoration did not significantly influence the restored tooth's overall strength and performance in the face of crack or debonding situations.

SIGNIFICANCE

The findings of this study have substantial implications for designing and restoring class II OD cavities to enhance resistance to cracks or debonding. The use of curved marginal geometries in restoration design can significantly improve fracture resistance, with double-curved geometries reducing stress concentrations by approximately 43% compared to straight cavities. These results offer valuable guidance for strengthening the structural integrity of restored teeth, calling for further experimental investigations to explore practical applications and benefits.

Understanding the Complexities of Cast Post Retention: A Comprehensive Review of Influential Factors

This comprehensive review delves into the intricate landscape of cast post retention in restorative dentistry, encompassing historical perspectives, contemporary techniques, and future directions. Examining factors ranging from tooth-related considerations to prosthesis-related dynamics, the review provides a detailed analysis of clinical techniques, including step-by-step procedures, common challenges, and innovative advancements. Technological breakthroughs, such as digital impressions, computer-aided design and computer-aided manufacturing (CAD/CAM) technology, three-dimensional (3D) printing, and finite element analysis, are explored for their transformative impact on precision and customization. The discussion extends to the promising future of cast post retention, emphasising emerging materials, the integration of artificial intelligence in treatment planning, and patient-specific approaches. Implications for clinical practice underscore the importance of individualised treatment planning and the adoption of advanced technologies. Recommendations for future research advocate for comprehensive long-term clinical studies, investigations into AI-driven treatment planning, and a focus on patient outcomes and satisfaction. This review consolidates existing knowledge and anticipates a future marked by enhanced precision, individualised care, and improved long-term success in cast post-retained restorations.

Clinical performance of direct composite resin versus indirect restorations on endodontically treated posterior teeth: A systematic review and meta-analysis

STATEMENT OF PROBLEM

High-level evidence concerning the restoration of endodontically treated posterior teeth by means of direct composite resin or indirect restorations is lacking.

PURPOSE

The purpose of this systematic review and meta-analysis was to analyze the current literature on the direct and indirect restoration of endodontically treated posterior teeth.

MATERIAL AND METHODS

Databases MEDLINE, CENTRAL, and EMBASE were screened. Risk of bias was assessed by using the ROB2 tool for RCTs and the ROBINS-I tool for prospective and retrospective clinical studies. Randomized clinical trials (RCTs) and prospective and retrospective studies comparing direct composite resin and indirect restorations on endodontically treated posterior teeth were included. Outcomes were tooth and restoration survival. A meta-analysis was conducted for tooth retention and restorative success.

RESULTS

Twenty-two studies were included (2 RCTs, 3 prospective, and 17 retrospective). Over the short term (2.5 to 3 years), low-quality evidence suggested no difference in tooth survival. For the prospective and retrospective clinical trials, the overall risk of bias was serious to critical from the risk of confounding because of a difference in restorative indication: Direct restorations were fabricated when one marginal ridge remained or when tooth prognosis was unfavorable. For short-term restorative success, low-quality evidence suggested no difference between the direct and indirect restorations.

CONCLUSIONS

For the short term (2.5 to 3 years), low-quality evidence suggests no difference in tooth survival or restoration quality. To assess the influence of the type of restoration on the survival and restorative success of endodontically treated posterior teeth, clinical trials that control for the amount of coronal tooth tissue and other baseline characteristics are needed.

In-Vitro Comparison of Fracture Strength of Endocrowns and Overlays in Endodontically Treated Teeth Manufactured with Monolithic Lithium Disilicate and Zirconia

To evaluate the fracture strength and the failure mode of endodontically treated molars restored with monolithic lithium disilicate and zirconia endocrowns and overlays. A total of 48 extracted mandibular molars were endodontically treated, decoronated 2 mm above the cementoenamel junction and divided into four 12-specimen groups. Group ELD: lithium disilicate endocrowns. Group EZ: monolithic zirconia endocrowns. Group OLD: lithium disilicate overlays. Group OZ: monolithic zirconia overlays. Overlays did not extend in the pulp chamber and endocrowns extended in the pulp chamber 2 mm. After adhesive bonding of the restorations, the specimens were subjected to thermocycling (×5000 cycles) and then to fracture resistance testing at lateral static loading (1 mm/min) at a universal testing machine. The failure mode of the specimens was qualitatively evaluated. Differences in means were compared using with t-tests for independent samples or Mann-Whitney test (p < 0.05). Weibull distribution analysis was also performed. Group ELD showed significantly higher fracture strength than all other groups (p = 0.001), and the highest Weibull modulus. Conclusions: Lithium disilicate endocrowns exhibit higher fracture strength and are more reliable compared to the other types of restorations examined. Endocrowns had more catastrophic failures compared to overlays.

Evaluation of mechanical properties of different polyetheretherketone endodontic post systems: an in vitro study

BACKGROUND

Survival of endodontically treated teeth depends on an efficient restoration of the missing tooth structure.

OBJECTIVES

This study aimed to investigate the mechanical properties of different endodontic post systems.

MATERIALS AND METHODS

Human permanent maxillary central incisors (no.=58) were decoronated and root-filled. The specimens with prepared root canals were randomly divided into Group P: Polyether Ether Ketone (PEEK) post and composite core and Group C: custom-made post-core of PEEK. The cementation of the posts was carried out using self-adhesive resin cement. Nano-hybrid composite resin was used for core fabrication. After cementation, the specimens from each group were randomly divided into two subgroups according to the types of tests utilized: 14 from each group were for the fracture strength test, which was restored with IPS e-max CAD crown, and 15 from each group for the pullout resistance test. A universal testing machine was used for the test performance.

RESULTS

The fracture resistance test showed that the values significantly differed among tested posts (P = 0.013). Group P showed the highest fracture resistance. Group C exhibited higher mean pullout resistance values than the other group (P) (P = 0.059). In the two-piece PEEK post and composite core, the predominant type of failure was a core fracture, while in the one-piece PEEK post-core, most types of failures were either in the crown or in the post.

CONCLUSIONS

The prefabricated posts are more resistant to fracture than the custom-made posts, with fracture and displacement mainly of the core. In contrast, both showed similar pullout resistance.

Effect of Dental Glass Fiber Posts on Root Stresses and Fracture Behavior of Endodontically Treated Maxillary Central Incisors: A Finite Element Analysis Study

OBJECTIVE

 In this work, the influence of glass fiber posts with different designs on the root stress that had endodontic treatment was examined using the finite element method.

METHOD

 Using two distinct materials (metal and glass fiber) and two different prototypes (tapered and parallel-sided), four three-dimensional (3D) finite element models of an upper central incisor were made and studied. Each 3D model received an oblique loading of 100 N. All forces were dispatched as distributed pressure to the aforementioned region. There were no considerations made for potential stresses when performing the endodontic procedure. The endodontic treatment was conducted without taking into account any potential stressors. The root stresses were then recorded.

RESULTS

The largest tensile stress is often focused at the apical third of the post and post/cement contact, as well as at the coronal third of the root on both the labial and palatal sides of the root, independent of the post's design and material. Restoration of endodontically treated maxillary central incisors with glass fiber posts has been shown to have less stress concentration than titanium posts. Regardless of the post materials employed, the tapered post design generated a higher tensile stress distribution than the parallel side design.

CONCLUSIONS

 Prefabricated fiber posts used in model restoration resulted in more evenly distributed stress and less concentrated stress on the root. Reduction in modulus of elasticity of post materials used generally shows less stress concentration.

Finite element analysis of endodontically treated premolars without ferrule restored with one-piece glass fiber post and core in combination with different inner shoulder retention form systems

OBJECTIVE

The current study was performed to explore the impact of post materials as well as the inner shoulder retention form (ISRF) design on the biomechanical behavior of endodontically treated premolars without ferrule restoration using a method of mathematical three-dimensional (3D) finite element analysis (FEA).

METHODS

Based on the tooth anatomy and our previous research, eight mandibular second premolar FEA models representing different restorative situations were built: teeth with (a) 2.0 mm height ferrule (DF), (b) no ferrule (NF), (c) 0.5 mm width and 0.5 mm depth ISRF (ISRFW0.5D0.5), (d) 0.5 mm width and 1.0 mm depth ISRF (ISRFW0.5D1.0), (e) 0.5 mm width and 1.5 mm depth ISRF (ISRFW0.5D1.5), (f) 1.0 mm width and 0.5 mm depth ISRF (ISRFW1.0D0.5), (g) 1.0 mm width and 1.0 mm depth ISRF (ISRFW1.0D1.0), (h) 1.0 mm width and 1.5 mm depth ISRF (ISRFW1.0D1.5). All groups were restored with prefabricated glass fiber post and resin composite core (PGF), one-piece glass fiber post-and-core (OGF) and cast Co-Cr alloy (Co-Cr) respectively, and the zirconia crown was restored. Load (180N) was subjected to the buccal cusp at 45° to the tooth's long axis. Stress pattern, maximum principal stress values (MPS), and maximum displacement values on root, post and core, cement layer were calculated for each model.

RESULTS

Stress distributions were similar while the values were different among groups. Regardless of restorative approaches, roots restored with PGF showed the highest MPS values, followed by OGF and Co-Cr groups. Regardless of post materials, NF groups resulted in the highest MPS values and maximum displacement values, while ISRF and DF groups exhibited similar results. Compared with PGF groups in association with ISRF, except for OGF with ISRFW0.5D0.5, the remaining OGF groups with ISRF and all Co-Cr groups in association with ISRF presented lower values than that of DF groups. And among different ISRF systems, roots restored with ISRFW1.0D1.0 presented the lowest stress (PGF: 32.96 MPa, OGF: 31.69 MPa, Co-Cr: 29.66 MPa).

CONCLUSIONS

For endodontically treated premolars without ferrule, restored with OGF in combination with ISRF preparation could effectively enhanced its load-bearing capacity. Furthermore, the ISRF with a depth and width of 1.0 mm is recommended.

Effect of sodium/calcium hypochlorite on adhesion and adaptation of fiber posts luted with a dual resin cement

This study aimed to evaluate the effect of different concentrations of sodium hypochlorite (NaOCl) and calcium hypochlorite [Ca(OCl)2] on the bond strength and adaptation of glass fiber posts luted with a dual-curing resin cement. Fifty decoronated premolars were sectioned 14 mm from the apex and endodontically treated. The root canal filling was partially removed. The specimens were divided into 5 groups (n=10) according to the irrigant for post space irrigation: 0.9% sodium chloride (NaCl), (control); 2.5% NaOCl; 5.25% NaOCl; 2.5% Ca(OCl)2; and 5.25% Ca(OCl)2. For each group, irrigation was performed with 5 ml of solution. Afterward, the posts were luted with a dual-curing resin cement. One slice from each third was obtained and submitted to the push-out test and failure modes analysis. An additional slice from the middle third was submitted to confocal images for analysis of adaptation failures (gaps). Two-way ANOVA, Tukey's post-hoc, Kruskal-Wallis with Bonferroni adjusted, and chi-square tests, analyzed data. The group treated with 5.25% NaOCl showed lower bond strength values and generated more cohesive failures compared to the control (p < 0.05). Bond strength decreased from coronal to apical in the post space (p < 0.001). The groups treated with NaOCl had the highest percentages of gaps compared to the control (p < 0.05). Regardless of concentration, Ca(OCl)2 did not influence the bond strength and the occurrence of gaps (P > 0.05). Ca(OCl)2 is a good option for irrigating the post space before luting a fiber post with a dual-curing resin cement.

Stronger than Ever: Multifilament Fiberglass Posts Boost Maxillary Premolar Fracture Resistance

This paper investigates the influence of cavity configuration and post-endodontic restoration on the fracture resistance, failure mode and stress distribution of premolars by using a method of fracture failure test and finite elements analysis (FEA) coupled to Weibull analysis (WA). One hundred premolars were divided into one control group (G_contr) (n = 10) and three experimental groups, according to the post-endodontic restoration (n = 30), G₁, restored using composite, G₂, restored using single fiber post and G₃, restored using multifilament fiberglass posts (m-FGP) without post-space preparation. Each experimental group was divided into three subgroups according to the type of coronal cavity configuration (n = 10): G_1O, G_2O, and G_3O with occlusal (O) cavity configuration; G_1MO, G_2MO, and G_3MO with mesio-occlusal (MO); and G_1MOD, G_2MOD, and G_3MOD with mesio-occluso-distal (MOD). After thermomechanical aging, all the specimens were tested under compression load, and failure mode was determined. FEA and WA supplemented destructive tests. Data were statistically analyzed. Irrespective of residual tooth substance, G₁ and G₂ exhibited lower fracture resistance than G_contr (p < 0.05), whereas G₃ showed no difference compared to G_contr (p > 0.05). Regarding the type of restoration, no difference was highlighted between G_1O and G_2O, G_1MO and G_2MO, or G_1MOD and G_2MOD (p > 0.05), whereas G_3O, G_3MO, and G_3MOD exhibit higher fracture resistance (p < 0.05) than G_1O and G_2O, G_1MO and G_2MO, and G_1MOD and G_2MOD, respectively. Regarding cavity configuration: in G₁ and G_2, G_1O and G_2O exhibited higher fracture resistance than G_1MOD and G_2MOD, respectively (p < 0.05). In G₃, there was no difference among G_3O, G_3MO and G_3MOD (p > 0.05). No difference was found among the different groups and subgroups regarding the failure mode. After aging, premolars restored with multifilament fiberglass posts demonstrated fracture resistance values comparable to those of an intact tooth, irrespective of the different type of cavity configuration.

Clinical longevity of extensive direct resin composite restorations after amalgam replacement with a mean follow-up of 15 years

OBJECTIVES

The aim of this retrospective clinical study was to determine the survival of extensive direct resin composite restorations after amalgam replacement on vital molars and premolars after a mean observation period of 15 years.

METHODS

Between January 2007 and September 2013, a total of 117 extensive cusp replacing direct resin composite restorations were placed in 88 patients in a general dental practice. These were indicated for replacement of existing amalgam restorations. Tooth vitality, the absence of at least one cusp in premolars, and at least two cusps in molars were considered for inclusion. The long-term follow-up of the restorations, re-evaluated after up to 17 years using the original evaluation criteria is reported.

RESULTS

81 of 88 patients (92.1%) and 106 of 117 restorations (90.6%) were available for follow-up. The cumulative success rate was 62.0% (95% CI: 47.3-76.2, AFR 2.79%) after a mean observation time of 163.4 months, the cumulative survival rate was 74.7% (95% CI: 59.8-89.6%, AFR: 1.70%) after a mean observation time of 179.1 months. The number of cusps replaced in premolars had a statistically significant influence on the success and survival rate of the restorations (HR of respectively, 2.974 and 3.175, p = <0.0005). Premolars with two cusps replaced had 297% more chance of failure than premolars with one cusp replaced.

CONCLUSIONS

Extensive direct resin composite restorations placed after amalgam replacement showed good survival after a mean observation period of 15 years. The number of cusps involved had a statistically significant influence on the longevity of the restorations in premolars.

CLINICAL SIGNIFICANCE

With good survival and low annual failure rates, direct resin composite restorations are a suitable treatment for repairing extensive defects in posterior teeth involving multiple cusps and surfaces, provided that they are placed by a dentist who has long experience and is skilled in the placement of direct composite materials.

Comparison of the measurement error of optical impressions obtained with four intraoral and one extra-oral dental scanners of post and core preparations

Statement of problem

Innovations in intraoral scanner (IOS) technology are opening up ever more indications for computer-aided design and manufacturing (CAD-CAM). The manufacturers claim that the latest generations of scanners allow the digitizing of root canal preparations. However, there is a lack of studies evaluating the quality of the optical impressions made for this type of treatment.

Purpose

The purpose of this study was to evaluate the measurement error of 4 IOSs and a laboratory scanner used for the digitizing of root canal preparations and to highlight the effect of the presence or absence of adjacent teeth on the quality of the digital model.

Material and methods

Two models: one presenting adjacent teeth, one without adjacent teeth, both presenting a 10 mm deep nominal conical pit mimicking a root canal preparation were fabricated. Each model was scanned 10 times with a laboratory scanner (E3) and 4 intraoral scanners (Primescan, Omnicam, TRIOS 4, and Medit i700). The digital models were then exported as standard tessellation language (STL) files and analyzed to evaluate the mean measurement error of the digitizing of the root preparation at three different depths: 0-3 mm, 3-6 mm, and 6-9 mm. Significant differences were assessed with a 1-way ANOVA test and the pairwise comparison between scanners was done by Tukey's multiple comparison test.

Results

Statistical differences were found between scanners (P < 0.05). The mean measurement error ranged from 9.8 ± 0.5 μm with the Medit i700 to 28.2 ± 10 μm with the E3. The E3 and Omnicam scanners were in some cases incapable of digitizing the conical preparation in its entirety. The group Primescan, TRIOS 4, and Medit i700 showed minimally significant differences. The presence of adjacent teeth had a negative effect on the model quality for some scanners, mainly because of the obstruction of the IOS's head.

Conclusions

Significant differences were found among the dental scanners used for digitizing root canal preparations. Optical impressions with modern intraoral scanners seem to be an adapted method of registration of root canal preparation for post-and-copings of post-and-cores fabrication.

Impact of different axial wall designs on the fracture strength and stress distribution of ceramic restorations in mandibular first molar

BACKGROUND

The purpose of this study was to investigate the fracture strength and stress distribution of four ceramic restorations.

METHODS

Forty human mandibular first molars were collected and randomized into four groups after establishing the distal defect: full crown group with 4 mm axial wall height (AWH) (FC4); short AWH crown group with 2 mm AWH (SC2); occlusal veneer group with 0 mm AWH (OV0); occlusal distal veneer group with only the distal surface prepared, and 4 mm AWH (OD4). The teeth were prepared according to the groups and the ceramic restorations were completed using celtra duo ceramic blocks. The ceramic thickness of the occlusal surface is about 1.5 mm and the edge is about 1 mm. The failure load values and fracture modes of each group were detected by mechanical test in vitro. According to the groups to establish three-dimensional finite element analysis (FEA) models, a 600 N loading force was applied vertically using a hemispherical indenter with a diameter of 6 mm. and compare the stress distribution under the condition of different restorations.

RESULTS

In vitro mechanical tests showed that the failure load values were SC2 (3232.80 ± 708.12 N) > OD4 (2886.90 ± 338.72 N) > VO0 (2133.20 ± 376.15 N) > FC4(1635.40 ± 413.05 N). The failure load values of the short AWH crown and occlusal distal veneer were significantly higher than that of occlusal veneer and full crown (P<0.05). The fracture modes of the full crown and occlusal veneer groups were mainly ceramic fractures and some were restorable tooth fractures. The short AWH crown and occlusal distal veneer groups presented with three fracture modes, the proportion of non-restorable tooth fracture was higher. The results of FEA show that under the spherical loading condition, the stress of ceramic was concentrated in the contact area of the loading head, the maximum von Mises stress values were FC4 (356.2 MPa) > VO0 (214.3 MPa) > OD4 (197.9 MPa) > SC2 (163.1 MPa). The stress of enamel was concentrated in the area where the remaining enamel was thinner, the maximum von Mises stress values was OD4 (246.2 MPa) ≈ FC4 (212.4 MPa) > VO0 (61.8 MPa) ≈ SC2 (45.81 MPa). The stress of dentin is concentrated in the root furcation and the upper third region of the root. However, stress concentration was observed at the tooth cervix in the full crown.

CONCLUSION

Under certain conditions, the occlusal distal veneer shows better performance than the full crown.

Safe and Ultraconservative Rehabilitation of Worn Teeth Patients: How Sectional Clear Aligners May Enhance the Prosthetic Treatment Plan

This study describes the clinical workflow for occlusal vertical dimension (OVD) increase in patients showing extensive tooth wear and mild teeth misalignment/crowding. A patient affected by dental erosion and occlusal abnormalities was treated to improve her situation. After ascertaining sound condyle and temporomandibular joint (TMJ) conditions, an OVD increase was sought to provide enough inter-occlusal space for the restorations. The use of TMJ three-dimensional imaging throughout the clinical procedures allowed to objectively track the condyle and disk position and confirm a steady condyle–glenoid cavity relationship before definitive restorations placement. Sectional clear aligner therapy prior to totally additive prosthetic rehabilitation allowed obtaining slight derotation and movements of anterior teeth, thus maximizing sound tissue preservation. Adhesively luted restorations were finally delivered on both anterior and posterior sectors. At the end of the treatment, the pre-operative TMJ balance appeared successfully preserved, and the patient was satisfied with the aesthetic and function achieved.

Present status and future directions: The restoration of root filled teeth

This narrative review will focus on a number of contemporary considerations relating to the restoration of root filled teeth and future directions for research. Clinicians are now more than ever, aware of the interdependence of the endodontic and restorative aspects of managing root filled teeth, and how these aspects of treatment are fundamental to obtaining the best long-term survival. To obtain the optimal outcomes for patients, clinicians carrying out endodontic treatment should have a vested interest in the restorative phase of the treatment process, as well as an appreciation for the structural and biomechanical effects of endodontic-restorative procedures on restoration and tooth longevity. Furthermore, the currently available research, largely lacks appreciation of occlusal factors in the longevity of root filled teeth, despite surrogate outcomes demonstrating the considerable influence this variable has. Controversies regarding the clinical relevance of minimally invasive endodontic and restorative concepts are largely unanswered with respect to clinical data, and it is therefore, all too easy to dismiss these ideas due to the lack of scientific evidence. However, conceptually, minimally invasive endodontic-restorative philosophies appear to be valid, and therefore, in the pursuit of improved clinical outcomes, it is important that the efficacies of these treatment protocols are determined. Alongside an increased awareness of the preservation of tooth structure, developments in adhesive bonding, ceramic materials and the inevitable integration of digital dentistry, there is also a need to evaluate the efficacy of new treatment philosophies and techniques with well-designed prospective clinical studies.

Finite element and in vitro study on biomechanical behavior of endodontically treated premolars restored with direct or indirect composite restorations

Objectives of the study were to investigate biomechanical properties of severely compromised premolars restored with composite restorations using finite element analysis (FEA), and in vitro fracture resistance test. A 3-D model of an endodontically treated premolar was created in Solidworks. Different composite restorations were modelled (direct restoration-DR; endo-crown-EC; post, core, and crown-C) with two different supporting tissues: periodontal ligament/alveolar bone (B), and polymethyl methacrylate (PMMA). Models were two-point axially loaded occlusally (850 N). Von Mises stresses and strains were calculated. The same groups were further tested for static fracture resistance in vitro (n = 5, 6.0 mm-diameter ball indenter, vertical load). Fracture resistance data were statistically analyzed (p < 0.050). The highest stresses and strains in all FEA models were observed on occlusal and vestibular cervical surfaces, corresponding to fracture propagation demonstrated in vitro. C showed the lowest stress in dentin, while EC showed lower stresses and strains in crown cement. B models demonstrated larger high stress areas in the root than PMMA models. No significant differences in fracture resistance (N) were observed between groups (DR: 747.7 ± 164.0, EC: 867.3 ± 108.1, C: 866.9 ± 126.3; p = 0.307). More conservative restorations seem a feasible alternative for endodontically treated premolars to conventional post-core-crown.

Deep Margin Elevation: A Literature Review

A conservative approach for restoring deep proximal lesions is to apply an increment of composite resin over the preexisting cervical margin to relocate it coronally, the so-called “deep margin elevation” (DME). A literature search for research articles referring to DME published from January 1998 until November 2021 was conducted using MEDLINE (PubMed), Ovid, Scopus, Cochrane Library and Semantic Scholar databases applying preset inclusion and exclusion criteria. Elevation material and adhesive system employed for luting seem to be significant factors concerning the marginal adaptation of the restoration. This technique does not affect bond strength, fatigue behavior, fracture resistance, failure pattern or repairability. DME and subgingival restorations are compatible with periodontal health, given that they are well-polished and refined. The available literature is limited mainly to in vitro studies. Therefore, randomized clinical trials with extended follow-up periods are necessary to clarify all aspects of the technique and ascertain its validity in clinical practice. For the time being, DME should be applied with caution respecting three criteria: capability of field isolation, the perfect seal of the cervical margin provided by the matrix, and no invasion of the connective compartment of biological width.

Patterns of Post-Endodontic Restoration: A Nationwide Survey of Dentists in Turkey

Developments in materials and techniques, geographical locations, age, specialty, and affiliations of dental practitioners affect the preference of post-endodontic restoration. Thus, this survey aimed to evaluate the trends of dentists in Turkey in terms of post-endodontic restorations. An anonymous survey containing 10 questions regarding demographics, post-endodontic restoration patterns, and factors affecting restoration selection was electronically delivered to the dentists registered in the database of the Turkish Dental Association. The data were analyzed using by a chi-square test and ordinal logistic regression analysis. A total of 1093 surveys from 20,564 participants were collected with a response rate of 5.3%. Half of the participants (52%) preferred composite resins for post-endodontic restorations. Usage of posts was less prevalent amongst prosthodontists and dentists with clinical experience of more than 20 years compared to endodontists (p < 0.001) and dentists with clinical experience of less than 5 years (p = 0.004). More than half of the participants (56%) utilized fiber posts. Composite resins and fiber posts were the most common preferences in post-endodontic restoration. Endodontists had a higher tendency to use posts than prosthodontists and general dental practitioners.

Five-to-five clear aligner therapy: predictable orthodontic movement for general dentist to achieve minimally invasive dentistry

Background

Esthetic dentistry has become a very important aspect of every dental treatment from the patient perspective, whether it is orthodontics or implant therapy. The aim of this article is to describe the advantages of a newly developed branch of five-to-five clear aligner therapy (CAT) (Invisalign Go, Align Technology, San Jose, Calif) in interdisciplinary treatments especially in terms of minimally invasive interventions.

Case presentation

Two case reports are presented together with a comprehensive analysis using the SAFE (Safety, Assessment, Function, Ethics) assessment. This paper aims to introduce a new systematic in CAT. Invisalign Go (Align Technology, Santa Clara, California, USA) allows orthodontic treatment from second premolar and second premolar in both arches. It is specially designed for general practitioners devoted to restorative dentistry for a better planning of a multidisciplinary and mini-invasive treatment plan.

Discussion and conclusion

The clinical results demonstrate how CAT is extremely useful in multidisciplinary treatment plan in order to straighten teeth especially in a pre-restorative phase to allow minimally invasive and adhesive restorations.

Push-out bond strength and failure mode of single adjustable and customized glass fiber posts

Purpose

To evaluate the push-out bond strength (PBS) and failure mode of single adjustable (SAP) and customized (CP) posts cemented to root canal dentin using conventional (RelyX Ultimate) or self-adhesive (RelyX U200) dual-cure resin cements.

Methods

Herein, 40 bovine mandibular incisors were divided into four groups (n = 10): SAP cemented with RelyX Ultimate (SAP-UT), SAP cemented with RelyX U200 (SAP-U2), CP cemented with RelyX Ultimate (CP-UT), and CP cemented with RelyX U200 (CP-U2). PBS and failure modes were analyzed. Three-way repeated measures ANOVA test followed by Tukey’s test and Fisher–Freeman–Halton exact test were used for data analysis (α = 5%).

Results

The PBS values for SAP (p < .05) were higher than those for CP and were not influenced by the root third and resin cement (p > .05). When conventional resin cement was used, the SAP showed significant differences compared to CP (p < .05). When cemented with RelyX Ultimate, a higher prevalence of mixed and adhesive failures for SAP and CP, respectively, was observed (p < .05). For the self-adhesive resin cement, the failures were mostly adhesive (p < .05).

Conclusion

SAP showed better performance than CP. The root third and resin cements did not influence the PBS. The most prevalent failures were adhesive and mixed.

Post-Fatigue Fracture and Marginal Behavior of Endodontically Treated Teeth: Partial Crown vs. Full Crown vs. Endocrown vs. Fiber-Reinforced Resin Composite

Objectives: To investigate in vitro post-fatigue fracture behavior of endodontically treated molars having been differently restored. Methods: A total of 120 extracted human molars were used. A total of 120 specimens in 14 test groups and one control group (n = 8) were root canal treated. After postendodontic sealing and build-up (AdheSE Universal, SDR), additional MOD preparations were cut. Postendodontic restorations were: Direct restorations (Tetric EvoCeram BulkFill bonded with AdheSE Universal and EverX Posterior/Essentia bonded with G-Premio Bond; as filling (F) or direct partial crown (DPC) after reducing the cusps 2 mm; indirect adhesive restorations (partial crown/PC vs. full crown/FC): e.max CAD, Celtra Duo, both luted with Variolink Esthetic; indirect zirconia restorations (partial crown/PC vs. full crown/FC), luted with RelyX Unicem 2; indirect non-bonded cast gold restorations (partial crown/PC vs. full crown/FC; Degunorm), luted with Ketac Cem. Before and after 300,000 thermocycles (5/55 °C) and 1.2 Mio. A total of 100 N load cycles, replicas were analyzed under a SEM for marginal quality in enamel and dentin (where applicable) and finally, specimens were loaded until fracture. Results: In direct groups, there was no difference between RC and FRC in fracture strength (p > 0.05); however, direct partial crowns showed higher post-fatigue fracture resistance. Regarding marginal quality, intracoronal FRC restorations exhibited more gap-free margins in enamel than RC. In the indirect groups, there was no significant difference between partial and full crowns in any of the adhesively luted ceramic groups regarding post-fatigue fracture resistance. Zirconia partial crowns exhibited significantly lower marginal quality in enamel. Indirect groups performed significantly better than direct groups in fracture resistance. Within the indirect restorations, both cast gold groups and zirconia full crowns exhibited the highest fracture resistance being superior to control teeth. Significances: Within the limits of this in vitro investigation, it can be concluded that any kind of indirect restoration with cusp replacement is suitable for ETT restoration when a certain cavity extension is exceeded. All indirect restorations, i.e., endocrowns, partial crowns, and full crowns showed a promising performance after in vitro fatigue-loading.

A Critical Review of the Differential Diagnosis of Root Fracture Line in CBCT scans

The objective of this critical review of literature is to discuss relevant clinical factors associated with root fractures (RF) visualized by using a new CBCT software. RF constitutes a common occurrence and a challenge in clinical practice, in which the diagnosis becomes essential for the definition of rapid and precise decision-making. The characterization of RF may involve different aspects, such as orientation of the fracture line (horizontal, vertical, oblique), root position of the fracture (cervical, middle, apical third), fracture's coronal-radicular position (coronary, coronal-radicular, radicular), continuity of the fracture (crack, incomplete fracture, complete), bone extension of the fracture (supraosseous, bone level, infraosseous fracture). Imaging examinations have been routinely used to aid in the RF diagnosis. Even with high-resolution cone-beam computed tomography (CBCT) scans, many doubts often remain about the diagnostic outcome. Many interferences in the analysis of image quality to determine the diagnosis are identified, such as the sharpness, the noise, light and dark artifacts, among others. The professional's knowledge is essential for identifying the different patterns of fracture lines and their repercussions on adjacent bone tissues, as well as for the analysis of artifacts that may hide or show similarities to fracture lines. Fractures lines and root fractures that may be associated with phantom conditions that mimic fractures should be carefully analyzed. CBCT is the exam indicated to identify a root fracture. It is also added to the success of the diagnosis that the professional has scientific knowledge, training and mastery of advanced CBCT software.

Treatment Prognosis of Restored Teeth with Crown Lengthening vs. Deep Margin Elevation: A Systematic Review

Crown lengthening surgery and deep margin elevation are two distinct approaches used to manage decayed teeth. This systematic review examined the survival rate of badly decayed teeth when restored using the crown lengthening technique and compared it to the deep margin elevation technique. The search was conducted during July 2020 and then again updated at the end of July 2021, and no restriction concerning publication status and time was applied during the search. Cochrane Database, EBSCO, Scopus, and Medline databases were searched electronically for relevant literature. Google Scholar was used as a secondary source. Predefined inclusion and exclusion criteria were used to select the relevant articles. PRISMA guidelines were followed. The focused PICO question was: 'Does the crown lengthening technique (I) provide a better survival rate (O) than deep margin elevation technique (C) following the restoration of badly decayed teeth (P).' A total of six articles were included after performing screening based on the eligibility criteria. Four studies focused on crown lengthening while two focused on deep margin elevation technique. A majority of the studies showed a high risk of bias owing to methodological insufficiencies. Crown lengthening (CL) treated cases showed a change in the free gingival margin at six months post-surgery. A tissue rebound was seen that was correlated to the periodontal biotype. Teeth treated with the deep margin elevation (DME) technique showed high survivability. There is a lack of high-quality trials examining surgical comparisons between CL and DME with long-term follow-up. Patient- and dentist-reported outcomes have not been given adequate consideration in the literature. Based on the limited evidence, it can be concluded that for restorative purposes, crown lengthening surgery can be successful in long-term retention of restored teeth. However, the deep margin elevation technique has a better survival ratio. Future well-designed and executed research will have an effect on the evidence and level of certainty for the best approach to treating severely decayed teeth.